Physical and chemical properties
1. Density. After cold deformation, the density of aluminum profiles
decreases due to the microcracks, macrocracks and holes in the cracks in and between grains.
2. Resistance. The destruction of intergranular material leads to the direct contact of grains, the ordination of grain direction, and the fracture of intergranular and intra granular, all of which have obvious influence on the change of electrical resistance. The first two make the resistance decrease with the increase of deformation degree, the latter is the opposite.
3. Chemical stability. After cold deformation, the internal energy of the material increases, making its chemical properties more unstable and easy to be corroded, especially easy to produce stress corrosion.
After cold deformation of aluminum profile, due to the intra - and intergranular failure, lattice distortion and the second type of residual stress, the plasticity index drops sharply and may be close to the completely brittle state in the limit state. On the other hand, due to lattice distortion, dislocation increase, grain is elongated and refined and the appearance of substructure, so that the strength index is greatly improved, that is, work hardening phenomenon.
Structure and anisotropy
After large cold deformation, the aluminum profiles show anisotropy due to the texture. For example, aluminum alloy sheet is prone to obvious lugging during deep drawing. Processing conditions should be reasonably controlled to make full use of the favorable aspects of texture and anisotropy, while avoiding or eliminating the unfavorable aspects.